Cutting tools made of ceramics, cermet or cemented carbide are usually coated with hard coatings to improve wear resistance and cutting performance. The coatings are usually optimized with respect to different applications. This optimization is often based on the predominant wear mechanism of the particular application. For example, alumina is known to improve resistance to crater wear on the rake side and different refractory metal nitrides, carbides and carbonitrides such as titanium carbonitride are known to improve resistance to abrasive wear on the clearance side. By forming coatings comprising different layers with different properties, the resistance to wear on different parts of the cutting tool and due to different wear mechanisms can be further improved, and with sophisticated tailoring of composition, microstructure, layer thickness, etc. improved performance for a certain application can be achieved. However, this approach remains a compromise between the wear and performance characteristics with respect to different parts of the cutting tool. As a solution to this different post treatments have been used.
U.S. Pat. No. 5,861,210 discloses a cutting tool coated with a multi-layered wear resistant coating including an outermost Ti(C,N,O) or Zr(C,N) layer deposited on an α-Al2O3 layer. The outermost layer is mechanically removed by means of brushing, grinding, polishing or blasting, either from only the cutting edge or from both the rake side and the cutting edge, so that the underlying α-Al2O3 layer is exposed, in order to simultaneously improve wear resistance of rake side and clearance side, and in particular the flaking resistance.
U.S. Pat. No. 5,776,588 discloses a cutting tool coated with a multi-layered wear resistant coating including e.g. an innermost TiCN, an intermediate Al2O3 layer and an outermost TiN layer. The TiN layer and the Al2O3 layer are removed by mechanical means such as a vibratory tumbling, brushing, shot blasting, grinding from the cutting edge, so that the innermost TiCN layer is exposed, in order to improve the resistance to chipping of the coating at the cutting edge.
U.S. Pat. No. 7,431,747 discloses a cutting tool coated with a multi-layered wear resistant coating including a aluminum oxide layer deposited on a hard material layer. The aluminum oxide layer is selectively removed by means of laser treatment from at least a portion of the clearance side so that the underlying hard material layer is exposed in order to eliminate disadvantages of having aluminum oxide layers on the clearance side and thereby avoid increase in the width of the wear mark on the clearance side and retention of the resistance to crater wear on the rake side.